1. Field of the Invention
The present invention relates to an electronic control unit for suppressing electric wave noise induced in a power supply line and a signal line.
2. Description of the Related Art
Heretofore, in order to suppress noise in an electronic apparatus, there has often been employed a method of inserting capacitors between a signal line and a ground line, and between positive and negative power supply lines.
As regards a conventional magnetic signal detecting device, in a magnetic signal detecting device utilized in a mobile communication apparatus such as a mobile telephone or a cordless telephone, an output signal from a magnetic resistance element constituted by a resistance bridge is grounded by employing a structure in which a non-inverted input terminal of a diffractive type operational amplification circuit constituted by a first operational amplifier and a second operational amplifier is grounded through a capacitor to enhance a noise resistance property, thereby preventing malfunction (refer to JP 11-202037 A for example).
In addition, in a conventional semiconductor integrated circuit device, circuit blocks are disposed in the order of increasing noise level between a power supply input terminal and a ground wiring and bypass capacitors are disposed in the respective circuit blocks to reduce an inductance component, thereby preventing an increase in impedance in a high frequency region is prevented to absorb power supply noise (refer to JP 2002-043525 A for example).
In the magnetic signal detecting device disclosed in JP 11-202037 A, a suitable capacity of the capacitor to be inserted is not specified. As a result, there has been a problem in that the responsibility to a detection signal becomes worse when the capacitance value is excessively large, while the noise cannot be suppressed sufficiently when the capacitance value is too small.
In addition, in the semiconductor integrated circuit device disclosed in JP 2002-043525 A, there is shown only a condition in which a wiring impedance is much larger than an internal parasitic inductance of the capacitor. Thus, there has also been encountered a problem in that the suitable capacitance values of the bypass capacitors are not clear.
Moreover, as to the noise resistance property of the electronic apparatus against the electric wave noise, the noise resistance property against the strong transmitted electric wave from the portable wireless apparatus such as a mobile telephone or a transceiver which is used in a nearby style is more important as compared to the noise resistance property against the received electric waves having various frequency bands. However, the magnetic signal detecting device disclosed in JP 11-202037 A and the semiconductor integrated circuit device disclosed in JP 2002-043525 A are incapable of handling this problem.